Such a layer, e.g. a layer of hydrogenated amorphous carbon, of the hard type (Diamond-Like Carbon (DLC)) or of the soft type (Polymer-Like Carbon (PLC)) is conventionally formed by Plasma-Enhanced Chemical Vapor Deposition (PECVD). This technology is well explained in the Applicant's European Patent No EP 1 068 032.
For example, when a soft carbon (PLC) is implemented, the preferably used precursor gas is acetylene (C3H2). This gas is injected into the container, inside which a partial vacuum (about 0.1 millibars (mbar)) has been formed, and then the plasma is activated, i.e. the acetylene is caused to go into a cold plasma state, by means of a Ultra-High-Frequency (UHF, (2.45 gigahertz (GHz))) low-power electromagnetic excitation. Among the species that are generated, there is to be found hydrogenated carbon (with CH, CH2 and CH3 bonds) which is deposited in a thin layer (of a thickness of about 1600 angstroms) on the polymer substrate formed by the inside wall of the container.
This method is conventionally conducted in a machine comprising:                a processing unit receiving the container and equipped with an electromagnetic wave generator for activating the plasma from a precursor gas;        a precursor gas inlet;        an injector for injecting said precursor gas into the container, said injector having a bottom end that opens out into the container and an opposite top end; and        a precursor gas feed duct that puts the precursor gas inlet into fluid flow connection with the top end of the injector.        
According to the method shown in FIG. 1, which is a graph showing how the pressure inside the container varies over time:                the container, as formed previously by blowing or by stretch-blowing, is mounted on a moving top portion of the processing unit, and then the unit is closed, the top portion coming to rest in leaktight manner on a bottom portion including an enclosure that receives the container;        by means of a vacuum pump, a partial vacuum is formed inside the container, for a length of time t0 of several seconds (approximately in the range 1 second (s) to 2 s);        the inside of the container is then swept with the precursor gas for a time t1 of about 1 s, the effect of this sweeping being to fill the container with precursor gas while also expelling the air still present (in FIG. 1, “O” is used for “open” and “C” for “closed”);        the plasma is then activated by bombardment with microwaves, for a time t2 varying in the range 1 s to 2 s, or even better in the range 1 s to 3 s, depending on the thickness of the internal barrier layer that is intended to be obtained (in a container designed for receiving a carbonated beverage such as beer, the time t2 is in the range 2 s to 3 s; for still beverages such as tea, said time t2 is approximately in the range 1 s to 1.5 s);        the residual gases coming from the plasma are then removed for a time t3 of about 0.1 s; and        finally, the container is removed from the processing unit.        
The processing of the container, comprising all of the above-described steps, takes several seconds (this length of time is assumed to be the sum of the times t0 to t3 plus the times taken to load and to unload the container), and is practically in the range 5 s to 7 s.
There is a perpetual need to increase the work rates. Unfortunately, today, it appears difficult to achieve any reduction in the times t0 to t3 or in the loading and unloading times.
However, the inventors do have a solution for reducing at least the time t1.
It should be noted, at this stage, that the amount of gas injected into the container is conventionally controlled by a pressure regulator (also acting as a flow meter) placed between the precursor gas inlet and the feed duct.